The present invention relates to a gear, more particularly, to the gear which has at least one longer tooth, shorter teeth and transition teeth.
In addition, the present invention relates to a fluid machine more particularly, to the fluid machine for conveying, compressing or expanding liquid or gaseous fluids, which has at least one gear pair according to the present invention.
In the prior arts in addition to be widely used as driving force transmission, the gear can also be used in many other fields. For example, a pair of gear-shaped rotors can be used as a gear pump to transport liquid fluids. However, the effective area used for fluid transferring by the rotors of the gear pump is relatively small, so the pumping efficiency is kept low. U.S. Pat. No. 3,574,491 discloses a gear-type rotary machine for transporting liquid fluid and compressing or expanding gaseous fluids, which consists of a housing and two engaging gear-shaped rotors being accommodated in the housing. Each gear includes two sets of shorter teeth alternating with one or more longer teeth. Because the two engaging gear-shaped rotors are provided with longer teeth, the effective area used for fluid transferring by the rotors of the gear pump is greatly increased. Unfortunately, when the longer teeth of the two rotors go to be near the inflection point of the xe2x80x9c8xe2x80x9d-shaped housing, because the profile of the longer tooth is not perfectly designed, the seal effect cannot be kept between the two longer teeth, resulting in a great amount of liquid backflow, thus the efficiency of the fluid transmission is caused at a low level, with nearly no function of compressing or expanding gas. In fact, although the two rotors keep engaging with each other, they are out of actual metallic contact with each other; additional torque transmitting gears have to be mounted outside so as to drive the shaft of the rotor, so the size of the rotor machine has to be increased.
U.S. Pat. No. 5,682,793 discloses an engaging rotor. When it is used for compressing gas, the gas in the tooth groove 3 of the rotor 1 cannot be compressed, only being moved from the inlet to the outlet. When the groove communicates with the compression chamber or the outlet, the gas is compressed at a constant volume, resulting in the power consumption increased and noise generated. When used for compressing gas, it becomes a rotor compressor with partial built-in compressing process. If every rotors are formed with a longer tooth and a longer tooth groove, when the longer teeth go to be near the inflection point of the xe2x80x9c8xe2x80x9d-shaped housing, the perfect seal effect cannot be realized, so some liquid will backflow and leak to the outside, thus the engaging rotor of this patent is inappropriate to be used in a compressor.
On the other hand, in the rotary compressors according to the prior art, the rotor compressors, the sliding-plate compressor, and the rotary vane compressor are all provided with the sliding-plates, the springs, the valves or the like which are easy to be damaged. The screw-rod compressor or the scroll compressor is simple in structure, but their curve surfaces are complex in shape, so it is difficult to be manufactured and checked. More particularly, in condition that those compressors are miniaturized, above-mentioned drawbacks are even worse. For the single tooth rotor compressor, the two rotors are out of actual metallic contact with each other, a clearance is kept between the corresponding engaging points of the two rotors. In such kind of compressor, a great of leakage between the two rotors can not be prevented, and it is difficult to make the compression ratio big enough. In fact, the single-stage compressor can only be used as an air blower. Because the rotors cannot transmit force to each other for their profiles, the angular position and the rotation of one rotor relative to another are controlled by a separate gear which can be synchronously rotated with said one rotor. The synchronous gear and its assembly make the compressor complex in structure and big in volume.
An object of the present invention is to provide a gear as a component of fluid compressing or expanding machine so as to transport fluid more efficiently.
Another object of the present invention is to provide a gear whose inertia force when used as a rotor can be cancelled out completely, although the teeth of which have different sizes with respect to each other.
A further object of the present invention is to provide a gear pair for reducing the leakage between the two engaging gears as rotors.
An additional object of the present invention is to provide a compressor or expansion machine, which has a complete built-in compression process, so its compression ratio can be obviously enhanced, so that the single-stage compressor can also be used as the compressor for generating pressured gas and the compressor for refrigerator, without over compression and under compression.
Another object of the present invention is to provide a fluid machine which have a perfect sealing effect.
A gear pair according to the present invention are formed as at least two gear-shaped rotors that engage with each other, so that the driving force can be transmitted. The driving gear and the driven gear are provided with shorter teeth, transition teeth and at least one longer tooth on their pitch circles respectively. The cross-section of the longer tooth is of a hawk beak shape, and the profile of the longer tooth is smoothly connected one after another by a convex section of the longer tooth, a tip section of the longer tooth, a concave section of the longer tooth and a leading section of the longer tooth. A transition tooth is provided on each of the two sides of the longer tooth. Each transition tooth is provided in neighborhood relationship with the longer tooth on one side thereof and a shorter tooth on the opposite side thereof. That is, the teeth of gear according to this invention is distributed in the order of a shorter tooth, a transition tooth, a longer tooth, the other transition tooth, and another shorter teeth.
An external engaging gear pair according to the present invention comprises at least two gear-shaped rotors that engage with each other. The two rotors are provided with shorter teeth, transition teeth and at least one longer tooth on their pitch circles respectively. The shaft of the driving rotor and the shaft of the driven rotor are arranged to be parallel to each other. The center to center distance from the driving rotor to the driven rotor is equal to the radial sum of the pitch circles of the two rotors. The cross-section of the longer tooth is of a hawk beak shape, the profile of the longer tooth is composed of a convex section, a tip section, a concave section and a leading section of the longer tooth, which are smoothly connected one to another in series. The longer tooth is connected at its two sides to the shorter teeth via transition teeth.
At least one gear pair according to the present invention is formed as two gear-shaped rotors that engage with each other. One of the two rotors is an internal gear, and another is an external one, the two rotors are provided with shorter teeth, transition teeth and at least one longer tooth on their pitch circles respectively. The shaft of the driving rotor and the shaft of the driven rotor are arranged to be parallel to each other. The center to center distance from the driving rotor to the driven rotor is equal to the radial difference of the pitch circles of the two rotors. The cross-section of the longer tooth is of a hawk beak shape, the profile of the longer tooth is composed of a convex section of the longer tooth, a tip section of the longer tooth, a concave section of the longer tooth, and a leading section of the longer tooth. The four sections of the longer tooth are smoothly connected one to another in series, so as to form the profile of the longer tooth. The convex section of the longer tooth of the internal gear projects into the inside of the pitch circle of the internal gear, while the leading section thereof recesses into the outside of the pitch circle. The convex section of the external gear projects into the outside of the pitch circle of the external gear, while the leading section thereof recesses into the inside of the pitch circle. Two transition teeth are respectively provided at the two sides of the longer tooth between the longer tooth. Each transition tooth is in neighborhood relationship with the longer tooth on one side thereof and a shorter tooth on the other side thereof.
According to another aspect of the present invention, the external engaging gear-type compressor includes a casing which is composed of an xe2x80x9c8xe2x80x9d-shaped housing, an tipper end cover and a lower end cover. At least one pair of engaging gear-shaped rotors are accommodated in the casing, and each pair of engaging gear-shaped rotors include one driving rotor and one driven rotor. An gas inlet is provided on the casing, and at least one gas outlets are provided on the end covers. The driving rotor and driven rotor are provided with shorter teeth, transition teeth and at least one longer tooth on their pitch circles respectively. The cross-section of the longer tooth is of a hawk beak shape, and the profile of the longer tooth is composed of a convex section, a tip section, a concave section and a leading section. The four sections are smoothly joined together in a manner of one after another, so as to form the profile of the longer tooth. The two sides of longer tooth are both adjacently provided with a transition tooth which in turn adjoins a shorter tooth. An elementary volume is enclosed by the longer teeth of the rotors, the engaging point, the wall of the housing, the upper end cover, and the lower end cover. When the gear-type compressor operates, the elementary volume varies periodically. When the elementary volume increases, the elementary volume communicates with the gas inlet, while when the elementary volume reduces, the elementary volume communicates with the gas outlet, so as to accomplish a complete working process of a suction, a compression and an evacuation.
According to another aspect of the present invention, the internal engaging gear-type compressor includes a casing which comprises a cylinder, an upper end cover, and a lower end cover. A shims in a shape of a part of moon is accommodated in the casing. The shim occupies the superfluous portion of the rotating space of the driving and driven rotors. At least one pair of internal engaging gears which include one driving rotor and one driven rotor are provided within the casing. Gas inlet and gas outlet are provided on the end covers. The driving rotor and the driven rotor are provided with shorter teeth, transition teeth and at least one longer tooth on their pitch circles respectively. The cross-section of the longer tooth is of a hawk beak shape, and the profile of the longer tooth is composed of a convex section, a tip section, a concave section and a leading section. The four sections of the longer tooth are smoothly connected one after another, so as to form the profile of the longer tooth. The convex section of the external gear projects into the outside of the pitch circle of the external gear, while the leading section recesses into the inside of the pitch circle thereof. The convex section of the internal gear projects into the inside of the pitch circle of the internal gear, while the leading section thereof recesses into the outside of the pitch circle. The two sides of the longer tooth are both provided with a transition tooth which adjoins a shorter tooth in turn. An elementary volume is enclosed by the longer teeth of the two rotors, the engaging point, the upper and the lower end covers, and the shim. When the gear-type compressor operates, the elementary volume varies periodically. When the elementary volume increases, the elementary volume communicates with the gas inlet, while when the elementary volume reduces, the compression starts, then the elementary volume communicates with the gas outlet, so as to accomplish a complete working process of a suction, a compression and an evacuation.
1. The two rotors keep engaging with each other, so that the driving force is directly transmitted from the driving rotor to the driven rotor while the working medium is perfectly sealed. In this way, the compressor can be simplified in structure, and the components of the compressor can be minimized.
2. The two rotors are both provided with the shorter teeth, the transition teeth and the longer teeth. Since the longer tooth is higher than the shorter tooth many times, the space between the rotors and the surrounding housing becomes larger, so that more effective area used for transferring fluid by the rotor of the gear pump can be used to transfer, compress or expand more working medium during one rotating working process of the rotors. As the effective area used for transferring fluid by the rotor of the gear pump is increased, the working efficiency of the gear pump is also improved.
3. For the external engaging gear-type compressor, when the tip sections of the longer teeth of the two rotors passes the edge of the gas inlet, an elementary volume is enclosed by the longer teeth of the two rotors, the engaging point, the wall of the xe2x80x9c8xe2x80x9d-shaped housing, and the upper and the lower end covers. In the compressor, the working medium is compressed so as to have a high-pressure. A clearance between the tip sections of the longer teeth of the two rotors and the housing is used to seal the working medium (the so-called slit seal solution). When the tip section of the longer tooth of the driving rotor reaches to the inflection point of the xe2x80x9c8xe2x80x9d-shaped housing, the tip section of the longer tooth of the driven rotor also reaches to the inflection point of the xe2x80x9c8xe2x80x9d-shaped housing. Once the tip sections of the longer teeth of the two rotors begin to disengage with the wall of the xe2x80x9c8xe2x80x9d-shaped housing, the tip section of the longer tooth of the driving rotor begins to engage with the starting point of the concave section of the longer tooth of the driven rotor. At this time, the tip section of the longer tooth of the driving rotor engages with the concave section of the longer tooth of the driven rotor, so that the working medium is kept being sealed. As no gap is appeared in the engaging point between the two rotors when the longer teeth of the two rotors disengage with the inflection point of the housing, the leakage of the working medium is prevented, so that the sealing effect can be kept during the complete working process. However, when the rotor with the traditional longer tooth profile is used, as the longer tooth of one gear engages with the longer tooth interval of the other gear, a gap is appeared between the high-pressure and low-pressure chambers when the longer teeth leave the inflection point of the xe2x80x9c8xe2x80x9d-shaped housing, resulting in a large amount of working medium backflow.
4. For the internal engaging gear-type compressor, when the tip section of the longer tooth of the driving rotor or the external gear passes the lower tip of the shim in the shape of a part of moon, an elementary volume is enclosed by the longer teeth of the two rotors, the engaging point of the two rotors, the shim in the shape of a part of moon, and the upper and the lower end covers. The working medium is sealed by means of the clearance provided between the longer teeth of the two rotors and the shim in the shape of a part of moon. Once the tip sections of the longer teeth of the driving and driven rotors reach to the upper tip of the shim in the shape of a part of moon, the tip sections of the longer teeth of the two rotors begin to disengage with the upper tip of the shim in the shape of a part of moon simultaneously. At the same time, the tip section of the longer teeth of the driving rotor is in engagement with the starting point of the leading section of the longer teeth of the driven rotor, so that an elementary volume is enclosed by the engaging point between the two rotors, the engaging point between the tip section of the longer tooth of the driving rotor and the concave section of the longer tooth of the driven rotor, and the upper and the lower end covers. In this way, no gap between the two longer teeth is appeared when the longer teeth of the two rotors pass through the upper tip of the shim in the shape of a part of moon, so that the perfect sealing effect is kept during the complete working process of a compression and an evacuation.
5. As the two rotors are in actual metallic engagement with each other, the fluid leakage between the two rotors can be minimum. In addition, as an oil injection technique is used, the fluid leakage through the clearance between the tip sections of the longer teeth and the housing and through other leakage passages can be greatly reduced, so that the volumetric efficiency is high and the compression ratio is also high.
6. All of the working medium in the closed elementary volume can be evacuated from the gas outlet, so no closed volume at the suction stage and/or closed volume at the discharge stage are remained in the compressor, so that the volumetric efficiency is improved.
7. When a rotor is provided with two or more longer teeth, since the longer teeth are symmetrically arranged with respect to the shaft of the rotor, the inertia force can be cancelled out completely. When the rotor is provided with only one longer tooth, the inertia force of the rotor can also be cancelled out completely by means of a balancing weight. As a result, the compressor can always be able to be kept a minimum vibration and noise.
8. In the prior art, the slip sheets, the spring and the valves as components of a compressor always subject to forces periodically varied, so they are liable to be damaged for fatigue reasons. In the present invention, however, no easily damaged components, such as the slip sheets, the spring and the valves, are arranged, so that the compressor seldom stop to work for the damage of the easily damaged components, thus the compressor according to the present invention is high in reliability.
9. Variant working conditions and variant capacity requirements can be conveniently met by means of regulating a slide valve, so as to help to save energy.
10. The rotor may be designed to have teeth which are perpendicular to the side surface of the rotor, so it is easier to manufacture the rotor.